So during our tests we monitor the voltage fluctuations as shown above in both IDLE and LOAD states of the PC. We write down the lowest and highest value we see.
That is the fluctuation, the baseline of the test. If a PSU is unstable we'd see much more fluctuation, differences and discrepancies which can result in system instability.
Once we gathered all results we can place them in an easy to understand chart. Look at the chart, the two lines show both the Idle and Load state of a specific voltage rail, the dark blue one the lowest voltage dip measured, the red one the highest fluctuation. That's your baseline.
The blue line you can't spot really, indicating that there's nothing going on instability wise.
ATX specification requires that the PSU stays within a 5% fluctuation, as such:
12 Volts should remain between 11.4 - 12.6v
As you can observe, the PSU when utilized and stressed stays stable with all fluctuations far within its safety margin, meaning that the PSU is functioning within ATX specified limits. During the load test, I several times checked to see if the PSU was warm; at 575~600+ Watts power draw, it was lukewarm at best. We do measure in an open chassis, always make sure you have good ventilation and airflow inside your chassis of course.
Sound levels (dBA)
As usual we grabbed our dBA meter, enabled the PSU by hot-wiring it and listening for any significant noise. Short and simple, it's really silent.
The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBA level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement.
As always we measure 75 CM away from the product (usually the distance between you and a desktop computer), and sure, this test will always a tad subjective.
We measured 38 dBA with the PSU activated and the system in IDLE. That's including surrounding noise levels (closed room with no audio sources), so that's just an okay result really.
We measured 39 dBA with the PSU activated and the system in STRESS consuming lots of current.
All in all, the noise level is hardly even hearable and far away from anything even remotely audible. Silent indeed.
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